\H{errors-hostkey-absent} \q{The server's host key is not cached in
the registry}
+\cfg{winhelp-topic}{errors.hostkey.absent}
+
This error message occurs when PuTTY connects to a new SSH server.
Every server identifies itself by means of a host key; once PuTTY
knows the host key for a server, it will be able to detect if a
If you see this message and you know that your installation of PuTTY
\e{has} connected to the same server before, it may have been
recently upgraded to SSH protocol version 2. SSH protocols 1 and 2
-use separate host keys, so when you first use SSH 2 with a server
-you have only used SSH 1 with before, you will see this message
+use separate host keys, so when you first use SSH-2 with a server
+you have only used SSH-1 with before, you will see this message
again. You should verify the correctness of the key as before.
See \k{gs-hostkey} for more information on host keys.
\H{errors-hostkey-wrong} \q{WARNING - POTENTIAL SECURITY BREACH!}
+\cfg{winhelp-topic}{errors.hostkey.changed}
+
This message, followed by \q{The server's host key does not match
the one PuTTY has cached in the registry}, means that PuTTY has
connected to the SSH server before, knows what its host key
... below the configured warning threshold}
This occurs when the SSH server does not offer any ciphers which you
-have configured PuTTY to consider strong enough.
+have configured PuTTY to consider strong enough. By default, PuTTY
+puts up this warning only for single-DES encryption.
See \k{config-ssh-encryption} for more information on this message.
terminate immediately after giving this error.
However, this error can also occur when memory is not running out at
-all, because PuTTY receives data in the wrong format. In SSH 2 and
+all, because PuTTY receives data in the wrong format. In SSH-2 and
also in SFTP, the server sends the length of each message before the
message itself; so PuTTY will receive the length, try to allocate
space for the message, and then receive the rest of the message. If
ridiculous amount of memory, and will terminate with an \q{Out of
memory} error.
-This can happen in SSH 2, if PuTTY and the server have not enabled
+This can happen in SSH-2, if PuTTY and the server have not enabled
encryption in the same way (see \k{faq-outofmem} in the FAQ). Some
versions of OpenSSH have a known problem with this: see
\k{faq-openssh-bad-openssl}.
bug in PuTTY. Please report it to us, and include the exact text
from the error message box.
-\H{errors-key-wrong-format} \q{Unable to use this private key file},
+\H{errors-cant-load-key} \q{Unable to use this private key file},
\q{Couldn't load private key}, \q{Key is of wrong type}
+\cfg{winhelp-topic}{errors.cantloadkey}
+
Various forms of this error are printed in the PuTTY window, or
written to the PuTTY Event Log (see \k{using-eventlog}) when trying
public-key authentication, or given by Pageant when trying to load a
This is almost certainly not a problem with PuTTY. If you see this
type of message, the first thing you should do is check your
-\e{server} configuration carefully. Also, read the PuTTY Event Log;
+\e{server} configuration carefully. Common errors include having
+the wrong permissions or ownership set on the public key or the
+user's home directory on the server. Also, read the PuTTY Event Log;
the server may have sent diagnostic messages explaining exactly what
problem it had with your setup.
This error occurs when PuTTY decrypts an SSH packet and its checksum
is not correct. This probably means something has gone wrong in the
encryption or decryption process. It's difficult to tell from this
-error message whether the problem is in the client or in the server.
+error message whether the problem is in the client, in the server,
+or in between.
A known server problem which can cause this error is described in
\k{faq-openssh-bad-openssl} in the FAQ.
in the server, or in between.
If you get this error, one thing you could try would be to fiddle
-with the setting of \q{Miscomputes SSH2 encryption keys} on the Bugs
+with the setting of \q{Miscomputes SSH-2 encryption keys} on the Bugs
panel (see \k{config-ssh-bug-derivekey2}).
Another known server problem which can cause this error is described
abort}
This is a generic error produced by the Windows network code when it
-decides that your network connection is dead. For example, it might
+kills an established connection for some reason. For example, it might
happen if you pull the network cable out of the back of an
Ethernet-connected computer, or if Windows has any other similar
reason to believe the entire network has become unreachable.
may be able to improve the situation by using keepalives; see
\k{config-keepalive} for details on this.
+Note that Windows can produce this error in some circumstances without
+seeing a connection reset from the server, for instance if the
+connection to the network is lost.
+
\H{errors-connrefused} \q{Network error: Connection refused}
This error means that the network connection PuTTY tried to make to